Particle-beam device equipped with a foundation supported to permit swinging movement

ABSTRACT

A particle-beam device such as an electron microscope or the like has a column containing a beam generator and optical components and a foundation for carrying said column. The foundation is supported to permit swinging movement at a low characteristic frequency. A control center configured as a desk console is arranged on a platform separate from the foundation and having space sufficient for accommodating an operator of the particle-beam device. A flexible transmitting structure for connecting the control center with said column is also provided.

United States Patent [191 Ruska et al.

[ Mar. 25, 1975 3,361,398 1/1968 Brinkman ct a1. 248/18 OTHERPUBLICATIONS The Electron Microscope by E. F. Burton ct al. published byReinhold Publishing Corp., New York, 1946, page 225.

Primary Examiner-James W. Lawrence Assistant E.taminerC. E. ChurchAttorney, Agent, or FirmHerbert L. Lerner [57] ABSTRACT A particle-beamdevice such as an electron microscope or the like has a columncontaining a beam generator and optical components and a foundation forcarrying said column. The foundation is supported to permit swingingmovement at a low characteristic frequency. A control center configuredas a desk console is arranged on a platform separate from the foundationand having space sufficient for accommodating an operator of theparticlebeam device. A flexible transmitting structure for connectingthe control center with said column is also provided.

10 Claims, 5 Drawing Figures 1 PARTICLE-BEAM DEVICE EQUIPPED WITH AFOUNDATION SUPPORTED TO PERMIT SWINGING MOVEMENT [75] Inventors: ErnstRuska; Franz Stocklein, both of Berlin, Germany [73] Assignee:Max-Planck-Gesellschat't Zur Forderung Der Wissenschaften e.V.,Gottingen, Germany [22] Filed: Aug. 1, 1973 [21] Appl. No.1 384,754

Related U.S. Application Data [63] Continuation of Ser. No. 162,767,July 15, 1971,

abandoned,

[30] Foreign Application Priority Data Feb. 5, 1971 Germany 2106378 [52]U.S. Cl. 250/306, 250/311 [51 Int. Cl. H0lj 37/26 [58] Field of Search52/167, 749. 750; 73/430;

[56] References Cited UNITED STATES PATENTS 2,268,495 12/1941 Petty248/18 PATENTEB MR 251975 sum 1 or Hg. 1 I

PMENTEBHARZSISYS SHEET 2 OF 4 PATENIH] W 2 5 I975 SHEET u gr 4 Fllg. 4

PARTICLE-BEAM DEVICE EQUIPPED WITH A FOUNDATION SUPPORTED TO PERMITSWINGING MOVEMENT This is a continuation of application Ser. No.162,767, filed July 15, 1971, now abandoned.

Our invention relates to a particle beam device such as an electronmicroscope or the like equipped with a column containing the beamgenerator and the optical components. The particle beam device also hasa desklike control console and a base which can swing at a lowcharacteristic frequency.

In the development of the electron microscope it was early recognizedthat the resolutions obtainable with electron optics are substantiallyaffected by earth vibrations caused mostly by traffic and industry. Thisis especially the case for making photographic pictures of electronimages where long illumination times are required. With the advance ofimaging technology, which in the meantime has led to a resolutioncapability of only a few angstroms, the problem has taken onsignificance. Especially bending movements of the microscope column aredamaging, which occur because of horizontal swings of the earth or flooron which the microscope is placed. The suppression of such swingingmovements is especially difficult with microscopes having a high beamvoltage of more than 100 kV and the correspondingly greater columnlengths of several meters.

For the foregoing reasons, a 500 kV electron microscope including thecontrol console has already been placed on a heavy foundation. Thefoundation, on the one hand, is isolated against the floor by means ofrubber dampers. In this connection, reference may be hat to the Journalof Scientific lnstruments 1967, Vol. 44, starting at page 747,especially page 749. The foundation has a characteristic frequency ofapproximately 3 Hz. In this way, it is possible to reduce the frequencyof floor swings which amounts to approximately 13-15 Hz to a swingingmovement having a frequency of 3 Hz.

It is an object of our invention to improve the isolation for particlebeam apparatus of the above mentioned type against vibration thatoriginates in the region surrounding the apparatus.

It is another object of our invention to provide an arrangement forreducing the characteristic frequency with which the foundation uponwhich the microscope column is mounted swings in response to vibrationsemanating from environment of the microscope.

According to a feature of the invention, we provide an arrangementwherein only the column is carried on a foundation, whereas the controlconsole is located on a platform separated from the foundation. Theplatform includes space sufficient for accommodating an observer. Theconsole is connected to the column only by flexible transmission means.In the arrangement of the invention, the observer or operator himself isprevented either from his own movements or by actuating the controlconsole to transfer vibrations to the column. The observer can moveabout freely on the platform during the time a photographic picture ismade without having to fear that his movements might affect thesharpness of the picture.

The characteristic frequency of the foundation and column considered asa unit has a characteristic frequency of preferably at most 1 Hz, sothat the accelerations imparted to the parts of the column duringswinging movements are only very small. Making the characteristicfrequency this low has, in addition, the advantage that it is widelyseparated from the characteristic frequency of a bending movement of thecolumn, which can amount to approximately Hz, so that the foundationswinging movement can cause a bending movement of the column only withconsiderable damping.

In a preferred embodiment of the invention, the foundation ispendulum-like supported. The pendulum length can, for example, amount to10 meters, so that the frequency of swinging movement amounts toapproximately l/6 Hz. Vertical swings can be retarded by means of lowfrequency air springs, for example, less than 3 Hz.

The suspension of the unit consisting of the foundation and microscopecolumn in a manner similar to that of a gravity pendulum has in thesituation at hand an especially valuable characteristic. A bendingswinging movement of the column can only be initiated when portions ofthe column which lie at different elevations experience varioushorizontal accelerations. However, if the total height of the microscopecolumn over the foundation is small-relative to the pendulum length, theaforementioned accelerations are all the same in the finalapproximation, so that the parts of the column relative to each otherare subjected to only very small horizontal forces. If the foundation issuspended by several parallel lines, so that the microscope column witha pendulum swing undergoes a movement parallel to itself, these residualforces also are completely eliminated.

The quiet of the foundation can be further improved by surrounding theparticle beam apparatus by a double walled building whose walls areseparated from each other at the ceiling and on the sides by means of anintermediate air space. In this construction, the platform is joinedonly to the outer wall and the foundation is suspended from the ceilingof the inner wall. The suspension of the foundation is in this wayisolated from wind forces and floor pressures. The walls of the buildingare preferably anchored at least 10 meters deep in the earth, so thatthe amplitudes of vibrations generated on the earths suface aresubstantially reduced as they travel to the base of the inner wall.

According to another embodiment of the invention, the foundation canalso rest on one or more bending elastic columns which likewise shouldbe anchored at great depth under the earths surface, preferably at least10 meters.

The stability of the microscope column can be further increased by meansof a strengthening support for increasing rigidity mounted on thefoundation. Such a support is rigid and has a somewhat pyramidal orconical configuration. The rigid support is tightly connected to thecolumn at its lower end and embraces the column at its top end in theregion of the upper half of the column. lt is advantageous to dimensionthe portion of the rigid support gripping the upper half of the columnas a horizontally adjustable collar, which makes it possible to apply abending prestress to one side of the column. In this way, the fact canbe taken into account that the microscope column does not need to havethe same bending elasticity in all directions because of constructionreasons. If a bending pre-stress is imparted to the column in adirection in which the bending moment is a minimum, a deflection firstoccurs when the force produced by an outside vibration exceeds theprestressed force. The initiation of a bending swinging movement in thisdirection is then made more difficult.

Also, floor vibrations do not, as a rule, occur in the same magnitude inall directions. These vibrations more often can be especially intense ina definite direction according to the spacial relationships. Also, inthis instance, it is advantageous to impart a bending prestress to thecolumn in the direction of maximum vibration.

The invention will now be described with reference to the drawings,wherein:

FIG. 1 illustrates, in section, an elevation view of a double-walledtower-like building in which an electron microscope is arranged asrequired by the invention;

FIG. 2 illustrates an alternate embodiment of FIG. 1 in which themicroscope column is supported on a foundation secured in the earth vialong, slender columns",

FIG. 3 is a perspective view of an electron microscope illustrating thedisposition or supporting members including a strengthening support forthe microscope column;

FIG. 4 illustrates the upper portion ofa strengthening support forincreasing the rigidity of the microscope column; and

FIG. 5 illustrates a plan view of the portion of the strengtheningsupport shown in FIG. 4.

FIG. 1 illustrates, in section, a double-walled towerlike building inwhich the electron microscope is housed. The electron microscope in itstotality is designated by reference numberal 1 and comprises essentiallya column la and a desk-like control console 1b. These parts are notrigidly connected together mechanically. A column 1a contains typicallythe beam generator, the electron optical lenses and equipment forobserving and registering an image.

The two walls of the building are designated by reference numerals 5 and6, respectively. A walking platform 7 is connected by horizontal beamswith the outer wall 6. The beams pass, without touching, through theinner wall 5. The depth T with which the building 5, 6 is anchored inthe earth should, as is possible, be more than meters.

The column 10 of an electron microscope 1 is carried by a heavyfoundation by means of a plate 2 and three supports 3. The foundationcan weigh approximately 10 to metric tons and be suspended pendulouslyby several nylon lines 8 from the ceiling of the inner wall 5. For thispurpose, three nylon lines can be used, for example. The supports 3 andthe suspension of the foundation 4 pass, without touching, through thewalking platform 7. Low frequency air springs 9 can be arranged in thepullies of the nylon lines 8 for limiting or attenuating verticalswinging movements. The pendulum length L can, for example, amount to 10meters, so that the foundation 4 with the column la has a swingingmovementfrequency of approximately 1/6 Hz.

The control console 1b is carried by the walking platform 7 and thelatter also includes the observers place. Therefore, no vibration on themicroscope column is imparted by the movements of the observer on thewalking platform 7 or by actuating the control console lb, for example,by turning the positioning and adjusting knobs or by throwing switches.The control console lb is connected with the column 1a by means offlexible conductors. As conductors, in this connection, the

electrical conductors which, for example, are used for supplying currentto the lenses and for supplying the positioning motors are especially tobe considered. Also, mechanical movements can be undertaken, forexample, movement of the specimen table by means of flexible shaftswhich run between the control console lb and the column la. Also, thecooling water conduits which connect with the column la and which arenot directed via the control console lb should be as flexible aspossible. The prevacuum pump can be arranged on the Walking platform 7.It, too, is connected to the high vacuum pump arranged directly on thecolumn. The connection can be made with a flexible vacuum conduit, forexample, in the form ofa rubber hose or bendable corrugated tube.

Because the building 5,6 is double walled, with an intermediate airspace 10, the inner building wall 5 is protected against outside airmovements and ground movements. A wind force or ground force applied tothe outer wall 6 does not lead, therefore, to a vibration of the innerwall 5 from which the foundation 4 with the column 1a are suspended.

Beneath the foundation 4 is a concrete column 11 on which the foundation4 can be lowered. Above the microscope 1 there is an intermediateceiling 12.

For further stabilizing the microscope la, there is provided astrengthening support which includes essentially the plate 2, threestruts 13 and an annular member 14; this additional feature will beexplained below in connection with FIGS. 3 to 5.

In the embodiment according to FIG. 2', foundation 4 carries themicroscope column 1a as in FIG. 1. Here, however, the foundation issupported by several steel columns 20 which, for example, can be threein number and be in the form of rods or pipes. The steel columns 20 bendelastically and, therefore, make possible a swinging movement of thecomposite of the foundation 4 with the column 10. The steel beams 20 areanchored at a great depth, for example, 10 meters beneath the earthssurface. The mass of the foundation 4 and of the column 1a on the onehand, and the elastic return force of the steel columns 20 on the otherhand, are so dimensioned that the swinging movement period of theelastic pendulum corresponds to less than 1 Hz, for ex ample, l/5 Hz.The building 21 in which the micro scope 1 is arranged can, in thisinstance, consist ofonly one wall 21. The same reference numerals usedin FIG. 2 as used in FIG. 1 correspond to similar items in FIG. 1.

In FIG. 3, the electron microscope with its carrying members isillustrated in detail. Here the same features as appear in FIG. 1 aredesignated with the same reference numerals. The column is againdesignated by reference numeral la and the control console configured intwo parts is designated by reference numeral 1b. The plate 2, the threestruts l3 and the annular member 14 which surrounds the column 1a,conjointly constitute the already mentioned strengthening support whichhere takes the form of a tetrahedral. The struts 13 can be, for example,steel pipes. Bending movement of the column 1a is effectively suppressedif the annular member 14 grips the column at its upper half, forexample, at a location two-thirds the height of the column.

A table plate 15 can be joined to the control console 1b and arrangednot to touch the plate 2 to serve as a shelf or writing surface for theobserver.

FIGS. 4 and 5 show the upper portion ofthe strengthening support inelevation and plan view, respectively. Referring to FIG. 4, the annularmember 14 comprises two parts, namely a ring 14a, which is securedrigidly or tightly to the struts l3, and a collar 14b, which by means ofscrews 15 is adjustable in a horizontal direction with respect to theringv 14a. The collar 14b is joined tightly to the column by means oftwo conical clamping rings l6, l7 and screws 18. For a one sidedadjusting of the screws 15, the collar 14b can be shifted horizontallyin any desired direction. In this way, the column 1a can receive acorresponding bending prestress, which makes difficult, as alreadymentioned, an initiation of bending swing movements in the prestresseddirection by means of earth vibrations. The column la is secured tightlyto the plate 2 at its end cross section, see FIG. 3. The collar 14b can,by means of additional screws 19, be held in the desired position on thering 14a.

In the illustrated embodiments, the rigid strengthening support includesseveral struts 13 which are arranged in the form of a pyramid,especially a tetrahedral. Instead of this kind of configuration usingstruts, a conical covering or jacket, for example, preferably made ofmetal, can be used, whose lower edge is braced against the plate 2 andwhose upper edge is joined with the annular body 14.

While the invention has been described by means of specific examples andin specific embodiments, we do not wish to be limited thereto, forobvious modifications will occur to those skilled in the art, withoutdeparting from the essential features of the invention and within thescope of the claims annexed hereto.

We .claim:

1. A charged particle-beam device such as an electron microscope or thelike, comprising a column containing a beam generator, electron opticallenses and means for observing and registering an image, a foundationfor carrying said column, supporting structure for said foundation topermit swinging movement at a low characteristic frequency of not morethan 1 Hz, a platform, a control center configured as a desk console andarranged on said platform, said platform being separate from saidfoundation and having space sufficient for accommodating an operator ofthe particle-beam device, flexible transmission means for connectingsaid control center with said column, and pendular suspension means forpendulou'sly suspending said foundation from said supporting structure,said pendular suspension means including a plurality of parallel cables.

2. A charged particle-beam device according to claim 1, said suspensionmeans comprising low frequency air springs for attenuating verticalswinging claim 1, wherein a double wall building surrounds theparticle-beam device, the two walls of said building being mutuallyseparated by an intermediate air space at the top and sides of saidbuilding, and pendular suspension means for pendulously suspending saidfoundation from the ceiling of the inner wall of said building, saidplatform being joined to only the outer wall of said building, saidpendular suspension means including a plurality of parallel cables.

4. A charged particle-beam device according to claim 3, wherein said twowalls extend to a depth of at least 10 meters into the earth at thesides of said buildmg.

5. A charged particle-beam device according to claim 1, comprising arigid strengthening support braced against said foundation, said supporthaving a base joined to the lower end of said column and a top partembracing said column at its upper half portion.

6. A charged particle-beam device according to claim 5, said supportbeing configured so as to have a pyramidal shape.

7. A charged particle-beam device according to claim 5, said supportbeing configured so as to have a conical shape.

8. A charged particle-beam device according to claim 5 said top part ofsaid strengthening support comprising a collar, and adjusting meansengaging said collar for positioning said collar horizontally withrespect to said column for imparting a bending pre-stress to the latter.

9. A charged particle-beam device such as an electron microscope or thelike, comprising a column containing a beam generator, electron opticallenses and means for observing and registering an image, a foundationfor carrying said column and being supported to permit swinging movementat a low characteristic frequency of not more than 1 Hz, a platform, acontrol center configured as a desk console and arranged on saidplatform, said platform being separate from said foundation and havingspace sufficient for accommodating an operator of the particle-beamdevice, and flexible transmission means for connecting said controlcenter with said column, said foundation comprising a base portion andat least one vertical bar upon which the base portion rests, said barhaving elastically bendable characteristics.

10. A charged particle-beam device according to claim 9, said bar beinganchored in the earth to a depth of at least 10 meters below the earthssurface.

1. A charged particle-beam device such as an electron microscope or the like, comprising a column containing a beam generator, electron optical lenses and means for observing and registering an image, a foundation for carrying said column, supporting structure for said foundation to permit swinging movement at a low characteristic frequency of not more than 1 Hz, a platform, a control center configured as a desk console and arranged on said platform, said platform being separate from said foundation and having space sufficient for accommodating an operator of the particle-beam device, flexible transmission means for connecting said control center with said column, and pendular suspension means for pendulously suspending said foundation from said supporting structure, said pendular suspension means including a plurality of parallel cables.
 2. A charged particle-beam device according to claim 1, said suspension means comprising low frequency air springs for attenuating vertical swinging movements of the composite of said foundation and said column.
 3. A charged particle-beam device according to claim 1, wherein a double wall building surrounds the particle-beam device, the two walls of said building being mutually separated by an intermediate air space at the top and sides of said building, and pendular suspension means for pendulously suspending said foundation from the ceiling of the inner wall of said building, said platform being joined to only the outer wall of said building, said pendular suspension means including a plurality of parallel cables.
 4. A charged particle-beam device according to claim 3, wherein said two walls extend to a depth of at least 10 meters into the earth at the sides of said building.
 5. A charged particle-beam device according to claim 1, comprising a rigid strengthening support braced against said foundation, said support having a base joined to the lower end of said column and a top part embracing said column at its upper half portion.
 6. A charged particle-beam device according to claim 5, said support being configured so as to have a pyramidal shape.
 7. A charged particle-beam device according to claim 5, said support being configured so as to have a conical shape.
 8. A charged particle-beam device according to claim 5, said top part of said strengthening support comprising a collar, and adjusting means engaging said collar for positioning said collar horizontally with respect to said column for imparting a bending pre-stress to the latter.
 9. A charged particle-beam device such as an electron microscope or the like, comprising a column containing a beam generator, electron optical lenses and means for observing and registering an image, a foundation for carrying said column and being supported to permit swinging movement at a low characteristic frequency of not more than 1 Hz, a platform, a control center configured as a desk console and arranged on said platform, said platform being separate from said foundation and having space sufficieNt for accommodating an operator of the particle-beam device, and flexible transmission means for connecting said control center with said column, said foundation comprising a base portion and at least one vertical bar upon which the base portion rests, said bar having elastically bendable characteristics.
 10. A charged particle-beam device according to claim 9, said bar being anchored in the earth to a depth of at least 10 meters below the earth''s surface. 